Turbine Component Cooling Channel Mesh with Intersection Chambers

ABSTRACT

A mesh ( 35 ) of cooling channels ( 35 A,  35 B) with an array of cooling channel intersections ( 42 ) in a wall ( 21, 22 ) of a turbine component. A mixing chamber ( 42 A-C) at each intersection is wider (W 1,  W 2 )) than a width (W) of each of the cooling channels connected to the mixing chamber. The mixing chamber promotes swirl, and slows the coolant for more efficient and uniform cooling. A series of cooling meshes (M 1,  M 2 ) may be separated by mixing manifolds ( 44 ), which may have film cooling holes ( 46 ) and/or coolant refresher holes ( 48 ).

STATEMENT REGARDING FEDERALLY SPONSORED DEVELOPMENT

Development for this invention was supported in part by Contract No.DE-FC26-05NT42644, awarded by the United States Department of Energy.Accordingly, the United States Government may have certain rights inthis invention.

FIELD OF THE INVENTION

This invention relates to cooling channels in turbine components, andparticularly to cooling channels intersecting to form a cooling mesh ina turbine airfoil.

BACKGROUND OF THE INVENTION

Stationary guide vanes and rotating turbine blades in gas turbines oftenhave internal cooling channels. Cooling effectiveness is important inorder to minimize thermal stress on these airfoils. Cooling efficiencyis important in order to minimize the volume of air diverted from thecompressor for cooling.

Film cooling provides a film of cooling air on outer surfaces of anairfoil via holes in the airfoil outer surface from internal coolingchannels. Film cooling can be inefficient because so many holes areneeded that a high volume of cooling air is required. Thus, film coolingis used selectively in combination with other techniques.

Perforated cooling tubes may be inserted into span-wise channels in anairfoil to create impingement jets against the inner surfaces of theairfoil. A disadvantage is that heated post-impingement air moves alongthe inner surfaces of the airfoil and interferes with the impingementjets. Also, impingement tubes require a nearly straight airfoil forinsertion, but some turbine airfoils have a curved span for aerodynamicefficiency.

Cooling channels may form an interconnected mesh that does not requireimpingement tube inserts, and can be formed in curved airfoils. Thepresent invention improves efficiency and effectiveness in a coolingchannel mesh.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in the following description in view of thedrawings that show:

FIG. 1 is a transverse sectional view of a prior art turbine vane withimpingement cooling inserts.

FIG. 2 is a side view of a prior art curved turbine vane airfoil betweenradially inner and outer platforms.

FIG. 3 is a transverse sectional view of a prior art turbine airfoilwith mesh cooling channels.

FIG. 4 is a perspective view of the prior art turbine airfoil of FIG. 3.

FIG. 5 is a sectional view of a cooling channel mesh per aspects of theinvention.

FIG. 6 is a transverse sectional view of an airfoil per aspects of theinvention.

FIG. 7 is a sectional view of a series of two cooling meshes.

FIG. 8 is a perspective view of part of a casting core that forms aspherical mixing chamber per aspects of the invention.

FIG. 9 is a perspective view of part of a casting core that forms atruncated spherical mixing chamber per aspects of the invention.

FIG. 10 is a perspective view of part of a casting core that forms acylindrical mixing chamber per aspects of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a transverse sectional view of a prior art turbine airfoil 20Awith a pressure side wall 21, a suction side wall 22, a leading edge 23,a trailing edge 24, internal cooling channels 25, 26, impingementcooling baffles 27, 28, film cooling holes 29, and coolant exit holes30. The impingement cooling baffles are thin-walled tubes inserted intothe cooling channels 25, 26. They are spaced apart from the channelwalls. Cooling air enters an end of each impingement baffle 27, 28, andflows span-wise within the vane. It exits impingement holes 31, andimpinges on the walls 21, 22.

FIG. 2 is a side view of a prior art curved turbine vane airfoil 20Bthat spans between radially inner and outer platforms 32, 33. Theplatforms are mounted in a circular array of adjacent platforms, formingan annular flow path for a working gas 34 that passes over the vanes.This type of curved airfoil can make insertion of impingement baffles27, 28 impractical, so other cooling means are needed.

FIG. 3 shows a prior art turbine airfoil 20C with a pressure side wall21 and a suction side wall 22 and a cooling channel mesh 35. A coolantsupply channel 36 is separated from a coolant inlet manifold 37 by apartition 38 with impingement holes 39. Coolant jets 40 impinge on theinside surface of the leading edge 23, then the coolant flows 41 intothe mesh 35, and exits the trailing edge exit holes 30.

FIG. 4 shows a perspective view of the prior art turbine airfoil 20C ofFIG. 3. The mesh 35 comprises a first plurality of parallel coolingchannels 35A, and a second plurality of parallel cooling channels 35B,wherein the first and second plurality of cooling channels intersecteach other in a plane or level below a surface of the airfoil, formingchannel intersections 42. The cross-sectional shape of the coolingchannels may be either circular or non-circular, including rectangular,square or oval.

FIG. 5 shows a cooling mesh per aspects of the invention. Each channelintersection has a mixing chamber 42A, which may be spherical orcylindrical. The mixing chamber delays the coolant flow, increasing heattransfer, and it provides a space and shape for swirl, increasinguniformity and efficiency of cooling. The mixing chambers 42A have awidth W1 that is greater than a width W of each of the channels openinginto the chamber. Each cooling channel 35A, 35B may have a widthdimension W defined at mid-depth of the channel as shown in FIG. 9. Themid-depth may be defined by a geometric centerline 45 of the coolingchannel as shown in FIGS. 8-10. The mixing chambers may have equalperpendicular widths W1, W2, thus providing a chamber shape thatpromotes swirl. If the mixing chambers are spherical or cylindrical,then each width W1, W2 is a diameter thereof. The term “width” hereinrefers to a transverse dimension measured at mid-depth 45 of thechannels connected to the mixing chamber.

Spherical and cylindrical mixing chambers have spherical or cylindricalsurfaces 43B between the four channel openings in the chamber. Solidparts 43 of the wall 21, 22 separate adjacent mixing chambers 42A andmay have four channel surfaces 43A and four chamber surfaces 43B. Thus,the solid parts 43 may have eight surfaces alternating between straightchannel surfaces 43A and spherical or cylindrical surfaces 43B. Thisgeometry maximizes the surface area of the channels 35A, 35B for a givenvolume of the mixing chambers 42A, and provides symmetrical mixingchambers for swirl.

FIG. 6 is a sectional view of an airfoil per aspects of the invention.The cooling channel mesh 35 is formed in a layer below the surface ofthe walls 21, 22, as delineated by dashed lines. A coolant supplychannel 36 may be separated from a coolant inlet manifold 37 by apartition 38 with impingement holes 39. Coolant jets 40 may impinge onthe inside surface of the leading edge 23. Then the coolant flows 41into the mesh 35, and exits the trailing edge exit holes 30. The mesh 35may follow the design of FIG. 5. Periodic mixing manifolds 44 may beprovided along the coolant flow path in the walls 21, 22 for additionalspan-wise mixing. These mixing manifolds 44 are closed off at the topand bottom. Film cooling holes 46 may pass between a mixing manifold 44and an outer surface of the airfoil. Coolant refresher holes 48 maymeter coolant from the coolant supply channel 36 into the mixingmanifold 44. The refreshment coolant flowing into the manifold 44 notonly reduces the temperature of the bulk fluid, but it also providesmomentum energy along a vector for additional mixing within themanifold.

FIG. 7 is a sectional view of a series of two cooling meshes M1, M2,separated by a mixing manifold 44. A coolant inlet manifold 37 receivescoolant via one or more supply channels from the turbine cooling system.The coolant inlet manifold 37 may be a leading edge manifold as shown inFIG. 6. Or it may be at another location, such as the locations of themixing manifolds 44 shown in FIG. 6. Coolant 41 flows through the firstmesh M1, and then enters a mixing manifold 44, which may include filmcooling holes 46 and/or coolant refresher holes 48 as shown in FIG. 6.The coolant then flows through the second cooling mesh M2. This sequenceof alternating meshes and mixing manifolds 44 may be repeated. Finally,the coolant may exit through trailing edge exit holes 30 or it may berecycled in a closed-loop cooling system not shown.

The intersection angle AA of the first and second cooling channels 35A,35B may be perpendicular, or not perpendicular, as shown. Shallowerintersection angles provide more direct coolant flow between themanifolds 37, 44. An angle AA between 60° and 75° provides a goodcombination of coolant throughput and mixing, although other angles maybe used.

The meshes M1, M2 and/or the mixing chambers 42A-C may vary in size,density, or shape along a cooled wall depending on the heatingtopography of the wall. The mixing manifolds 44 may vary in spacing andtype for the same reason. For example, coolant refresher holes 48 may bespaced more closely on the leading half of the pressure side wall 21than in other areas. Likewise for film cooling holes 46. Both filmcooling holes and refresher holes may be provided in the same mixingmanifold 44 and they may offset from each other to avoid immediate exitof refresher coolant.

FIG. 8 illustrates part of a casting core that forms a spherical mixingchamber 42A by defining a volume that is unavailable to molten metalduring a casting process. FIG. 9 illustrates part of a casting core thatforms a spherical mixing chamber 42B that is truncated at opposite endsto the extent of depth range D of the channels 35A, 35B connectedthereto. Truncation allows thinner component walls 21, 22. FIG. 10illustrates part of a casting core that forms a cylindrical mixingchamber 42C with an axis 50 centered on the intersection and normal tothe outer surface of the wall 21, 22. The cylindrical mixing chamber maybe truncated to the depth range D of the connected channels 35A, 35B.

The mixing chambers may take shapes other than cylindrical or spherical.However, a cylindrical or spherical shape of the mixing chambers 42A-Cbeneficially guides the flow 41 into a circular swirl that providespredictable mixing, and maximizes the chamber volume while minimizingreduction of the channel length.

Herein, the term “cooling air” is used to mean any cooling fluid forinternal cooling of turbine airfoils. In some cases, steam may be used.The term “straight channel” or “straight span” means a channel orsegment thereof with a straight geometric centerline and without flaredor constricted walls.

While various embodiments of the present invention have been shown anddescribed herein, it will be obvious that such embodiments are providedby way of example only. Numerous variations, changes and substitutionsmay be made without departing from the invention herein. Accordingly, itis intended that the invention be limited only by the spirit and scopeof the appended claims.

What is claimed is:
 1. A turbine component comprising: a mesh of coolingchannels comprising an array of cooling channel intersections located ina wall of the turbine component; a mixing chamber located at each of aplurality of the cooling channel intersections; wherein: each mixingchamber comprises a width that is wider than a respective width of eachcooling channel connected thereto; each mixing chamber comprises firstand second widths that are perpendicular to each other and equal to eachother; and said two connected cooling channels define respectivelongitudinal axes that intersect the mixing chamber at an angle of 60 to75 degrees with respect to each other as viewed perpendicularly to aplane defined by at least one of said longitudinal axes.
 2. The turbinecomponent of claim 1, wherein each mixing chamber defines a shape thatis not cylindrical or spherical.
 3. The turbine component of claim 1,wherein the cooling channels of the mesh are straight between the mixingchambers of the mesh.
 4. The turbine component of claim 1, wherein eachmixing chamber extends only within a depth range of said connectedcooling channels.
 5. The turbine component of claim 1, wherein eachmixing chamber has a cylindrical or a spherical shape centered on therespective intersection and a diameter that is greater than therespective widths of the connected cooling channels.
 6. The turbinecomponent of claim 5, wherein each mixing chamber comprises a sphericalgeometry that is truncated at opposite ends thereof, limiting the mixingchamber to a depth range of said connected channels.
 7. The turbinecomponent of claim 5, wherein the mixing chambers of the mesh areseparated by solid portions of the wall, each solid portion comprisingeight surfaces, alternating between straight channel surfaces andspherical or cylindrical chamber surfaces.
 8. The turbine component ofclaim 1, further comprising a coolant inlet manifold along an inlet sideof said interconnected mesh and a coolant mixing manifold in the wall,wherein the coolant mixing manifold extends along both an outlet side ofsaid interconnected mesh and along an inlet side of a secondinterconnected mesh defined according to claim 1 within the wall.
 9. Theturbine component of claim 8, wherein the coolant mixing manifoldcomprises coolant refresher holes that meter a coolant into the coolantmixing manifold from a coolant supply channel in the turbine component.10. The turbine component of claim 8, wherein the coolant mixingmanifold comprises film cooling holes that meter a coolant from thecoolant mixing manifold to an outer surface of the wall.
 11. The turbinecomponent of claim 8, wherein the wall comprises film cooling holes thatmeter a coolant from the coolant mixing manifold to an outer surface ofthe wall and coolant refresher holes that meter the coolant into thecoolant mixing manifold from a coolant supply channel in the turbinecomponent, wherein the film cooling holes are offset from the coolantrefresher holes.
 12. The turbine component of claim 1, furthercomprising a refresher coolant inlet opening into each mixing chamberfor delivery of fresh coolant thereto.
 13. A turbine componentcomprising: a first plurality of parallel cooling channels located in alayer below a surface of a wall of the component, each cooling channelfrom said first plurality of parallel cooling channels defining arespective cooling channel longitudinal axis; and a second plurality ofparallel cooling channels located in said layer, each cooling channelfrom said second plurality of parallel cooling channels defining arespective cooling channel longitudinal axis; wherein: viewed along anaxis substantially perpendicular to said surface, each cooling channellongitudinal axis of the first plurality of parallel cooling channelsappears to intersect one or more cooling channel longitudinal axes ofthe second plurality of parallel cooling channels at an angle to definean interconnected mesh of the cooling channels comprising an array ofapparent intersections of the cooling channels, each intersectioncomprising a mixing chamber; each mixing chamber comprises a shape thatdefines an axis that is substantially centered on the intersection andnormal to said surface; and each mixing chamber has a diameter greaterthan a width of said each cooling channel of the intersection at amid-depth of the respective cooling channel.
 14. The turbine componentof claim 13, wherein a respective mixing chamber extends only within adepth range of said each cooling channel of the intersection.
 15. Theturbine component of claim 13, wherein the mixing chambers of the meshare separated by solid portions of the layer, each solid portioncomprising eight surfaces alternating between straight channel surfacesand spherical or cylindrical chamber surfaces.
 16. The turbine componentof claim 13, further comprising a coolant inlet manifold along an inletside of said interconnected mesh, and a coolant mixing manifold in thewall, wherein the coolant mixing manifold extends along an outlet sideof said interconnected mesh.
 17. The turbine component of claim 16,wherein the coolant mixing manifold comprises coolant refresher holesthat meter a coolant into the coolant mixing manifold from a coolantsupply channel in the turbine component.
 18. The turbine component ofclaim 16, wherein the coolant mixing manifold comprises film coolingholes that meter a coolant from the coolant mixing manifold to an outersurface of the wall.
 19. The turbine component of claim 16, wherein thewall comprises film cooling holes that meter a coolant from the coolantmixing manifold to an outer surface of the wall and coolant refresherholes that meter coolant into the coolant mixing manifold from a coolantsupply channel in the turbine component, wherein the film cooling holesare offset from the coolant refresher holes.
 20. A turbine airfoilcomprising: a first plurality of parallel cooling channels located in alayer below a surface of an outer wall of the airfoil, each coolingchannel from said first plurality of parallel cooling channels defininga respective cooling channel longitudinal axis; a second plurality ofparallel cooling channels located in said layer; , each cooling channelfrom said second plurality of parallel cooling channels defining arespective cooling channel longitudinal axis wherein: viewed along anaxis substantially perpendicular to said surface, each cooling channellongitudinal axis of the first plurality of parallel cooling channelsappears to intersect one or more cooling channel longitudinal axes ofthe second plurality of parallel cooling channels at an angle of 60 to75 degrees in a first interconnected mesh of the cooling channelscomprising an array of intersections of the cooling channels; eachintersection comprising a mixing chamber that is wider than each coolingchannel of the intersection at a mid-depth of said each cooling channelof the intersection; the cooling channels of the mesh are straightbetween the mixing chambers of the mesh; a coolant inlet manifoldlocated along an inlet side of said first interconnected mesh; a coolantmixing manifold located in the wall along an outlet side of said firstinterconnected mesh and along an inlet side of a second interconnectedcooling channel mesh within the layer; wherein: the coolant mixingmanifold comprises film cooling outlet holes or coolant refresher inletholes.